package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisData;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Resource
    private CacheClient cacheClient;

    public Result queryById(Long id) {

        //缓存穿透
        //Shop shop = queryWithPassThrough(id);
        Shop shop = cacheClient.queryWithPassThrough(CACHE_SHOP_KEY,id,Shop.class,this::getById,CACHE_SHOP_TTL,TimeUnit.MINUTES);

        //互斥锁缓存击穿
//        Shop shop = queryWithMutex(id);

        //逻辑过期解决
//        Shop shop = queryWithLogicExpire(id);
        if(shop == null){
            return Result.fail("店铺不存在");
        }

        //7.返回
        return Result.ok(shop);
    }


    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        if(id == null){
            return Result.fail("店铺不能为空");
        }

        //更新数据库
        updateById(shop);

        //删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + id);

        return Result.ok();
    }

    //设置锁
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    //删除锁
    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }

    public Shop queryWithPassThrough(Long id){
        String key = CACHE_SHOP_KEY + id;

        //1.从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在
        if(StrUtil.isNotBlank(shopJson)){
            //3.存在直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }

        //判断是否是空值 就是""
        if(shopJson != null){
            return null;

        }

        //4.不存在 根据id查询数据库
        Shop shop = getById(id);

        //5.不存在 返回错误
        if(shop == null){
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL,TimeUnit.MINUTES);
            return null;
        }

        //6.存在 写入redis
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);

        //7.返回
        return shop;

    }

    public Shop queryWithMutex(Long id){
        String key = CACHE_SHOP_KEY + id;

        //1.从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在
        if(StrUtil.isNotBlank(shopJson)){
            //3.存在直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }

        //判断是否是空值 就是""
        if(shopJson != null){
            return null;

        }

        //实现缓存重建

        //获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        Shop shop = null;
        try {
            boolean isLock = tryLock(lockKey);
            //判断是否成功
            if(!isLock){
                //失败休眠重试
                Thread.sleep(50);
                return queryWithMutex(id);
            }

            //4.不存在 根据id查询数据库
            shop = getById(id);

            //模拟重建延时
            Thread.sleep(200);

            //5.不存在 返回错误
            if(shop == null){
                //将空值写入redis
                stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL,TimeUnit.MINUTES);
                return null;
            }

            //6.存在 写入redis
            stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);

        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            //释放互斥锁
            unlock(lockKey);
        }
        //7.返回
        return shop;

    }

    //逻辑过期 装饰者模式
    public void saveShop2Redis(Long id,Long expireSeconds){
        //1.查询店铺数据
        Shop shop = getById(id);

        //2.封装逻辑过期
        RedisData redisData = new RedisData();

        redisData.setData(shop);

        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        //写入redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id,JSONUtil.toJsonStr(redisData));
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public Shop queryWithLogicExpire(Long id){
        String key = CACHE_SHOP_KEY + id;

        //1.从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在
        if(StrUtil.isBlank(shopJson)){
            //3.存在直接返回
            return null;
        }


        //4.存在 判断是否过期 先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);

        //未过期返回店铺信息 由于Redisdata里面封装的是Object 所以这里返回的是JSONObject
        Shop shop = JSONUtil.toBean((JSONObject) redisData.getData(), Shop.class);

        LocalDateTime expireTime = redisData.getExpireTime();
        //没有过期
        if(expireTime.isAfter(LocalDateTime.now())){
            return shop;
        }

        //过期 尝试互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
            boolean isLock = tryLock(lockKey);
            //判断是否成功
            if(isLock){
                CACHE_REBUILD_EXECUTOR.submit(() -> {
                    //重建缓存
                    try {
                        this.saveShop2Redis(id,20L);
                    } catch (Exception e) {
                        throw new RuntimeException(e);
                    }finally {
                        //释放锁
                        unlock(lockKey);
                    }
                });
            }
        //7.返回
        return shop;
    }
}
